Swift_Preferences::getInstance PHP Méthode

    public static function getInstance()
    {
        if (!isset(self::$_instance)) {
            self::$_instance = new self();
        }
        return self::$_instance;
    }

 /**
  * Send email using swift api.
  * 
  * @param $body
  * @param $recipients
  * @param $from
  * @param $subject
  */
 public function sendEmail($body, $recipients, $from, $subject)
 {
     $config = Zend_Registry::get('config');
     $failures = '';
     Swift_Preferences::getInstance()->setCharset('UTF-8');
     //Create the Transport
     $transport = Swift_SmtpTransport::newInstance($config->mail->server->name, $config->mail->server->port, $config->mail->server->security)->setUsername($config->mail->username)->setPassword($config->mail->password);
     $mailer = Swift_Mailer::newInstance($transport);
     $message = Swift_Message::newInstance();
     $headers = $message->getHeaders();
     $headers->addTextHeader("signed-by", Constant::EMAIL_DOMAIN);
     //Give the message a subject
     $message->setSubject($subject);
     //Set the From address with an associative array
     $message->setFrom($from);
     //Set the To addresses with an associative array
     $message->setTo($recipients);
     //Give it a body
     $message->setBody($body);
     $message->setContentType("text/html");
     //Send the message
     $myresult = $mailer->batchSend($message);
     if ($myresult) {
         return null;
     } else {
         return Constant::EMAIL_FAIL_MESSAGE;
     }
 }